Watershed is an ideal natural unit over which hydrological processes are integrated
and for which a water balance may be constructed to show the disposal of
precipitation into a number of subsequent forms i.e. interception, soil moisture and
ground storages, evapotranspiration and run-off. Also, the watershed approach is
logical for evaluating the biophysical linkages of upland and downstream
activities, this approach is holistic and environmental impacts can readily be
evaluated ( Eastern and Brooks, 1985 ).
Importance of upstream and downstream linkage
Upstream and downstream linkage is a unique feature for the management and
utilization of watershed resources. Conflicts between upstream and downstream
users of land, forest and water are on the rise because of limited access of poor
people to these resources.
It is not possible to ensure the long-term protection of downstream river banks and biodiversity without the conservation of upstream land. Eg, The Churia and Bhabar region is important for the ecological and economic development of the Terai region because it is the recharge zone for the groundwater of the Terai. This region receives higher rainfall than the Terai and Mid-hills and recharges aquafer crucial for agricultural productivity of the most densely populated region of Nepal. In Nepal, about one-fourth of the people live below the poverty line and lack access to good quality land and off-farm employment opportunities. Therefore, they are compelled to encroach on forests and pastures for fulfilling their basic needs of food, fodder and fuel. The increasing depletion of forests has destabilized the whole system to such an extent that the future of both the highlanders and lowlanders of Nepal is at risk.
The majority of poor people who live in the hills or the Terai of Nepal, or upstream
or downstream of any watershed, rely on agriculture for their employment.
Therefore, intensifying sustainable agriculture, and the PES mechanism, through technological and managerial
innovations, along with management of forest, land and water resources, continues
to be crucial to the people of Nepal to achieve the twin objectives of poverty reduction
and sustainable conservation.
The payment for environmental services (PES) is a noble mechanism in which
“providers” (or sellers) of environmental services are paid by consumers or beneficiaries
of these environmental services i.e the upland people are paid for changing or adopting appropriate land use, technology to help prevent deterioration of lowland resources and infrastructures. There is increasing interest in PES and incentive-based mechanisms with the growing demand for food, drinking water, and energy combined with pressure on natural resources in most parts of the world.
In Nepal, the PES of watershed system is implemented formally for the supply of drinking
water from the upstream (remote villages) to the downstream of highly populated areas,
e.g., Sundarijal water supply project for Kathmandu valley, Kathmandu Upatyaka
water supply project for Kathmandu valley, Dhulikhel water supply project for Banepa
and Dhulikhel in Kavre district, etc. Similarly, the watershed inhabitants are getting the
PES from large projects of Nepal Electrical Authority (NEA) for the conservation and
development of upstream watershed area of the project such as Kulekhani watershed
in Makawanpur district.